Basic Math MCP Server

A simple yet powerful MCP server built using the FastMCP framework that enables basic math operations like addition, subtraction, multiplication, and division — usable right inside Claude Desktop or any MCP-compatible environment.

What is MCP?

MCP (Model Context Protocol) is an open standard developed by Anthropic that allows external tools, APIs, or scripts to be exposed to large language models (LLMs) like Claude in a structured and interactive way.

With MCP, developers can:

• Build custom tools accessible by language models.
• Extend capabilities of Claude with Python scripts or microservices.
• Share structured data or custom responses via @tool() and @resource() decorators.

What is a Custom MCP Server?

A Custom MCP Server is a Python-based service that implements the MCP specification using the mcp-server library. These servers:

• Define callable tools (@tool) for computation or automation.
• Host resources (@resource) like documentation or reference data.
• Run locally or remotely, responding to MCP clients such as Claude Desktop.

MCP servers enable low-latency, secure, and contextual integration between your own code and the capabilities of LLMs.

What We’ve Built

This project is a minimal but complete MCP server offering basic arithmetic capabilities. Tools exposed:

Tools:

• add(a, b) – Returns the sum of two numbers.
• subtract(a, b) – Returns the result of subtracting b from a.
• multiply(a, b) – Returns the product of a and b.
• divide(a, b) – Returns the quotient of a divided by b. Handles division by zero.

Resources:

• calculator://help – A Markdown-formatted help file that explains usage of all tools.

Prerequisites

Before getting started, make sure you have the following installed:

• Python 3.9+
• Claude Desktop (or any MCP-compatible interface)
• uv runtime (for fast, isolated Python execution)

Installation Steps

Step 1: Install uv (required to run MCP servers)

macOS/Linux:

curl -Ls https://astro.build/install/uv | bash

This will install uv to ~/.local/bin/uv

Windows (PowerShell):

irm https://astro.build/install/uv.ps1 | iex

You may need to restart your terminal or add uv to PATH.

Step 2: Install the MCP Server

Use uv to install mcp-server and run your server:

uv pip install mcp-server

To run the server manually:

uv run mcp-server

Integration with Claude Desktop

Once installed, you need to configure Claude to discover this MCP server.

Locate claude_desktop_config.json

This file holds MCP server configurations for Claude Desktop. Add or update as below.

If You Don’t Have Any MCP Servers:

Paste this entire block into your config:

{
  "mcpServers": {
    "mcp-server": {
      "command": "uv",
      "args": [
        "run",
        "mcp-server"
      ]
    }
  }
}

If You Already Have MCP Servers:

Just add the following entry to the "mcpServers" object:

"mcp-server": {
  "command": "uv",
  "args": [
    "run",
    "mcp-server"
  ]
}

Make sure your JSON stays valid (e.g., commas between entries).

Usage Examples

This image illustrates how the Basic Math MCP Server works in real-time with Claude Desktop.

Tool Help Resource

You can also use the built-in help:

resource: calculator://help

It returns markdown-formatted instructions for all tools.

Useful Links

• PyPI: MCP-Server
• Claude + MCP Docs: Official Anthropic Guide
• GitHub UV Runtime: https://github.com/astral-sh/uv